Noise damping muffler



p 6 R. L. DILLS 2,764,342

NOISE DAMPING MUFFLER Filed Jan. 31, 1952 Inventor:

His Attorney.

Raymond L..Dills,'

United States Patent NOISE DAMPING MUFFLER Raymond L. Dills, Erie, Pa., assignor to General Electric Company, a corporation of New York Application January 31, 1952, Serial No. 269,292

4 Claims. (Cl. 230-232) My invention relates to refrigeration apparatus and pertains more particularly to refrigerating units.

One type of refrigerating unit comprises a sealed case housing a compressor and a motor for driving the compressor. The compressor draws in a mixture of vaporous refrigerant and oil, compresses it and exhausts it into a muffler from which it eventually exits into the case. The exhaust is in pulses and the mufiler dampens the pulses. This reduces substantially the transmission of exhaust noises to the case surrounding the compressor. However, some noises are still transmitted from the mufiier to the case and it is desirable that these noises be absorbed in order to reduce further sound transmission to the case.

Accordingly, it is the primary object of my invention to provide a more quietly operating refrigerating unit.

Another object of my invention is to provide in a refrigerating unit comprising a sealed case housing a compressor and a mufller for damping compressor exhaust pulses, an improved arrangement for absorbing exhaust noises not dampened by the muffler thereby to minimize transmission of sound to the case.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In carrying out the objects of my invention, I provide a refrigerating unit including a sealed case having an oil sump and housing a compressor. A muffler receives the exhaust from the compressor and dampens the noises resulting therefrom. A rim formed on the under side of the muffler extends into oil in the sump and causes refrigerant bubbles rising in the oil to be trapped against the under side of the muffler. The trapped bubbles serve to absorb sound. 7

For a better understanding of my invention, reference may be had to the accompanying drawing in which Fig. 1 is an elevational view, partly broken away, of a refrigerating unit incorporating an embodiment of my invention; and

Fig. 2 is a section taken along the lines 2--2 in Fig. l and looking in the direction of the arrows.

In Fig. 1 I have shown a refrigerating unit 1 including a sealed case 2. Housed in the lower part of the case 2 is a rotary compressor generally designated 3; and housed in the upper part of the case is a motor (not shown) for driving the compressor. The bottom of the case 2 constitutes an oil sump generally designated 4. The compressor includes an upper frame 5 and a lower frame 6 spaced apart by an annulus 7. The annulus 7 is located concentrically with respect to a crankshaft 8 attached to the drive shaft of the motor. The lower end of the crankshaft 8 bears on a thrust plate 9 secured to the under side of the lower frame 6 by screws 10. Along its length, portions of the crankshaft 8 bear in both the upper and lower frames 5 and 6, respectively.

Formed on the crankshaft 8 and in the same plane as the annulus 7 is an eccentric 11. As perhaps better seen ice in Fig; 2, the eccentric 11 carries rotatably thereon a rotor 12. In this arrangement, rotation of the crankshaft 8 effects an eccentric operation of the rotor 12 in the annulus 7. Formed in the annulus 7 is a radial slot 13. Positioned slidably in the radial slot 13 is a blade 14. A compression spring 15 is provided and has one end seated in a bore 16 in the outer end of the blade 14 and the other end positioned in a spring seat 17 formed in a bracket 18 suitably secured to the upper frame 5. The spring 15 causes the blade 14 to engage and follow the rotor 12 as it operates eccentrically in the annulus 7. Formed in the annulus 7 on one side of and adjacent the blade 14 is an intake port 19 to which is connected a suction line 29 from a refrigerating system (not shown). Formed in the annulus on the other side of the blade 14 is an exhaust port 21. The direction of rotation of the rotor 12 is such that a mixture of vaporous refrigerant and oil is drawn into the annulus from the system through the suction line 29 and the intake port 19. The mixture is compressed by the rotor and expelled through the exhaust port 21. The expulsion of the compressed mixture is in pulses which if not mufiled would result in transmission to the case 2 of substantial noise.

Provided for muffling the pulses and thereby reducing the transmission of exhaust noises to the case 2 is a muffler generally designated 22. The muffler 22 comprises three muffler chambers 23, 23a and 23b formed by the cooperation of a cover plate 24 with three downwardly opening recesses 25 in the under side of the lower frame 6 and separated from each other by webs 26. The cover plate 24 is secured to the under side of the lower frame 3 by means of screws 27 threaded into the webs 26. The muffler chamber 23 receives the exhaust mixture from the exhaust port 21. The exhaust mixture passes from the chamber 23 into the chambers 23a and 2312 through passages 28 formed in the webs 26. In this manner the exhaust sounds are substantially dampened.

Connected to the muffler chamber 23a is a tube 29. The tube 29 conducts the exhaust mixture to an annular chamber 30 formed about the upper frame 5. The chamber 30 is effective for assisting in damping the exhaust pulses. A passage 31 in the upper frame 5 and located diametrically opposite the tube 29 admits the exhaust mixture into a reservoir 32 also formed in the upper frame 5. In the annular chamber 30 and the reservoir 32 the vaporous refrigerant and oil separate. The refrigerant is conducted by means not shown through the upper part of the unit to an exhaust tube 33 through which it is exhausted from the case 2. A space 3011 between the upper frame 5 and the case 2 provides communication between the chamber 30 and the lower part of the case 2. The oil separated from the gas in the chamber 30 drains through the space 30a into the oil sump 4. The oil-separated from the gas in the reservoir 32 settles in the bottom of the reservoir as a reserve indicated by 34, in Fig. 1.

The oil 34 in reservoir 32 drains through a passage 35 connecting the bottom of the reservoir 32 with the radial slot 13. In this manner an oil film is maintained about the portion of the blade in the radial slot for lubricating and sealing the blade. Another passage 36 in the upper frame drains oil in excess of a predetermined level in the reservoir 32 into the oil sump 4. Drainage of oil from the chamber 39 and the overflow of oil from the reservoir 32 results in the maintenance of a reserve of oil indicated by 37 in the oil sump 4.

The above-mentioned thrust plate 9 is formed with an oil inlet hole 38 at the center. The lower end of the crankshaft 8 has a slot 39 machined across its bottom thrust bearing end. A spiral groove 49 is formed on the lower portion of the crankshaft 8 and communicates with the slot 39. When the crankshaft 8 rotates the slot 39 acts as a centrifugal pump, drawing oil from the reserve 37 through the oil inlet hole 38 and forcing it into the spiral groove 40. The spiral groove 40 conveys the oil to the under side of the eccentric i1. A vertical groove 41 in the eccentric 11 conducts the oil to the top side thereof. From the top of the eccentric 11, the oil is conveyed by a spiral groove 42 formed in the upper portion of the crankshaft 8 to the top of the upper frame and is dumped into the reservoir 32. In this manner the crankshaft S and eccentric 11 are lubricated and oil is supplied to the reservoir 33 for replenishing the reserve 34.

Some refrigerant is still mixed with the oil that is drained into the sump 4. This refrigerant tends to vaporize and rise as bubbles to the surface of the oil reserve 37 where it results in a foam or a layer of such bubbles. In order that pure oil will be drawn through the oil inlet hole 38, the above-mentioned thrust plate 9 is located deep enough in the reserve 37 as to be below the foam at the surface thereof.

While the described mufiler 22 reduces substantially the transmission of exhaust sounds to the case 2, it does not dampen all exhaust noises. It is desirable to absorb the remaining noises and thereby reduce further the transmission of sounds to the case. In order to accomplish this, I have provided an unbroken downwardly extending rim 43 on the outer periphery of the cover plate 24. At least the lower edge of the rim 43 is submerged in the oil 37. During operation of the compressor 3 the muffler 22 becomes heated by the exhaust mixture. Heat from the muffler accelerates the vaporization of the refrigerant and the formation of refrigerant bubbles in the oil 37. The rim 43 causes a multitude f the refrigerant bubbles rising in the oil 37 to be trapped against the under side of the mufller 22 or against the under side of the cover 24. This multitude of bubbles, indicated by 44- in Fig. 1, serves to absorb the unmullled exhaust noises.

It is to be understood that while the rim 43 is shown and described as being formed on the outer periphery of the cover plate 24 the invention is not limited to this specific construction. The rim could extend downwardly from the perimeter of the lower frame 6. Also, the muffler could be formed by means other than the cooperation of the cover plate with the recesses in the lower frame, in which case it would be essential only that a rim be formed on the under side of the muffler or in such a relationship thereto that refrigerant bubbles would be caused to be trapped against the under side of the muffler.

It is to be understood further that the submersion of at least the lower edge of the rim 43 in the oil 3'7 represents an optimum relationship between the rim and oil. It is possible that refrigerant bubbles or foam would be trapped against the under side of the muffler 22 even if the lower edge of the rim 4-3 were spaced slightly above the surface of the oil. This. however, would depend upon the thickness of foam on the surface of the oil. This thickness is not constant and, therefore, in order to insure entrapment of refrigerant bubbles against the under side of the muflier at least the lower edge of the rim 43 is submerged. Actually the normal level of the oil 37 in the sump 4 is such that substantially all of the mulller 22 is maintained submerged in the manner shown in Fig. 1. With the muffler 22 so submerged in the oil 37 full advantage is taken of the heat from the muffler for accelerating the formation of refrigerant bubbles in the oil and insuring the entrapment of bubbles against the under side of the muffler substantially immediately after the refrigerating unit commences operatmg.

While I have shown and described a specific embodiment of my invention, i do not desire my invention to be limited to the particular form shown and described and I intend by the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a refrigerating unit, a sealed case including a sump, a compressor enclosed in said case and adapted to compress a mixture of vaporous refrigerant and oil, a muffler having spaces therein for receiving the exhaust from said compressor and reducing transmission of sound to said case, and means providing communication between said mulller and said case for affording drainage of oil admixed with refrigerant into said sump, said mufl'ler including an unbroken downwardly extending marginal rim on the outer periphery of the under side thereof, at least the lower edge of said rim being submerged in oil in said sump, said rim trapping refrigerant bubbles rising in said oil in said sump aganst substantally all of said under side of said muiller adjacent said exhaust receiving spaces thereby to absorb sound from said muffler and reduce further the transmission of sound to said case.

2. In a refrigerating unit, a sealed case including a sump, a compressor enclosed in said case and adapted to compress a mixture of vaporous refrigerant and oil, a muffler having spaces therein for receiving the exhaust from said compressor and reducing transmission of sound to said case, said mufiler being heated by said exhaust, means providing communication between said muffler and said case for affording drainage of oil admixed with refrigerant into said sump, the under side of said muffler being submerged in oil in said sump, the heat from said mufiler effecting the formation of refrigerant bubbles in the oil against said under side of said muffler, and an unbroken downwardly extending marginal rim formed on the outer periphery of said under side of said muffler, said rim trapping said refrigerant bubbles formed against substantially all of said under side of said muffler adjacent said exhaust receiving spaces thereby to absorb sound from said mufiler and reduce further the transmission of sound to said case.

3. In arefrigerating unit, a sealed case including a sump, a compressor enclosed in said case adapted to compress a mixture of vaporous refrigerant and oil, said compressor including a downwardly opening recess, a cover cooperating with said recess to form a muffler chamber, said muffler chamber receiving the exhaust from said compressor and reducing transmission of sound to said case, and means providing communication between said muiller chamber and said case for affording drainage of oil admixed with refrigerant into said sump, said cover including an unbroken downwardly extending marginal rim on its outer periphery, at least the lower edge of said rim being submerged in said oil in said sump, said rim trapping refrigerant bubbles rising in said oil in said sump against substantially all of the under side of said cover adjacent said muffler chamber thereby to absorb sound from said muffler chamber and reduce further the transmission of sound to said case.

4. In a refrigerating unit, a sealed case including a sump, a compressor enclosed in said case adapted to compress a mixture of vaporous refrigerant and oil, said compressor including a downwardly opening recess, a cover cooperating with said recess to form a muffler chamber, said .mulller chamber receiving the exhaust from said compressor and reducing transmission of sound -to said case, said cover being heated by said exhaust,

means providing communication between said .mulller chamber and said case for affording drainage of oil admixed withrefrigerant into said sump, said cover being submerged in oil in said sump, the heat from said cover effecting the formation of refrigerant bubbles in the oil against substantially all of the under side of said cover adjacent said muffier chamber, and an unbroken downwardly extending marginal rim formed on the periphery of said cover, said rim trapping said refrigerant bubbles formed against substantially all of said under side of said cover adjacent .said mufiler chamber thereby to ab- 5 sorb sound from said muffler chamber and reduce fur- 2,243,465 ther the transmission of sound to said case. 2,597,243

References Cited in the file of this patent UNITED STATES PATENTS 5 877,709

2,200,222 Tarleton May 7, 1940 6 Kucher May 27, 1941 Hubacker May 20, 1952 FOREIGN PATENTS France Dec. 15, 1942 

